Comparative assessment of feeding damage by pod-sucking bugs (Heteroptera: Coreoidea) associated with cowpea, Vigna unguiculata ssp. unguiculata in Nigeria

Feeding trials were conducted on three (young, mid-fill and mature) developmental stages of cowpea Vigna unguiculata ssp. unguiculata pods in the screenhouse using fourth instar nymphs and adults of Anoplocnemis curvipes (Fabricius), Riptortus dentipes (Fabricius), Mirperus jaculus (Thunberg), Clavigralla tomentosicollis Stål and C. shadabi Dolling. Anoplocnemis curvipes was observed to be the most damaging coreoid species causing a yield reduction of 26.4–51.7% followed by R. dentipes (24.4–29.4%), M. jaculus (21.9–26.9%), C. tomentosicollis (17.9–22.4%) and C. shadabi (15.9–20.4%). The fourth instar nymphs of each pod-sucking bug species caused a significantly higher cowpea yield reduction than their respective adults. Similarly, infestation on young pods compared to mid-fill and mature stages resulted in significantly higher yield reduction. The results suggest that infestation levels of two fourth instar nymphs of A. curvipes or three fourth instar nymphs of the other four pod-sucking bug species per young pod should be adequate for screening of cowpea varieties for resistance to the coreoid bugs.

Egg parasitoids of hemipteran pests of cowpea in Nigeria and Tanzania, with Special reference to Ooencyrtus patriciae Subba Rao (Hymenoptera: Encyrtidae) attacking Clavigralla tomentosicollis Stål (Hemiptera: Coreidae)

Egg parasitoids attacking economically important pod-sucking Hemiptera on cowpea were collected in Nigeria and Tanzania. The three coreid hosts, Anoplocnemis curvipes (F.), Clavigralla tomentosicollis Stål and C. elongata Sign., and the two alydid hosts, Mirperus jaculus (Thnb.) and Riptortus dentipes (F.), form a pest complex that attacks grain legumes across Africa. Parasitoids attacking eggs of C. tomentosicollis were monitored on farmers' fields at a locality in northern Nigeria. Parasitism rose from low initial levels to maxima of 62% in 1978 and 51% in 1979. This mortality did not keep host populations below the economic injury level. The egg parasitoid complex of C. tomentosicollis was dominated by the scelionid Gryon gnidus (Nixon), while the encyrtids Ooencyrtus patriciae Subba Rao and O. kuvanae (How.) parasitised a large proportion of host eggs at times. Small numbers of Gryon fulviventris (J. C. Crawford) and the eupelmids Anas tatus spp. were reared. Observations on the biology and behaviour of O. patriciae are presented. This species occurred in both Tanzania and Nigeria and attacked all hosts studied. Rearings of all these parasitoids and also another species of Gryon, a species of Baeus and two species of Telenomus from eggs of the five species of Hemiptera are reported.